Nano-fabrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate; therefore nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems, and the like.
An exemplary nano-fabrication technique in use today is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. Patent Publication No 2004/0065976, U.S. Patent Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference.
An imprint lithography technique disclosed in each of the aforementioned U.S. patent publications and patent includes formation of a relief pattern in a formable liquid (polymerizable liquid) and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be coupled to a motion stage to obtain a desired positioning to facilitate the patterning process. The patterning process uses a template spaced apart from the substrate and a formable liquid applied between the template and the substrate. The formable liquid is solidified to form a rigid layer (a solidified layer) that has a pattern conforming to a shape of the surface of the template that contacts the formable liquid. After solidification, the template is separated from the rigid layer such that the template and the substrate are spaced apart. The substrate and the solidified layer are then subjected to additional processes to transfer a relief image into the substrate that corresponds to the pattern in the solidified layer.
In imprint technology, defects like sheared, pulled-out, and torn features may be observed in resulting imprinted patterns. A defect often occurs due to strain mismatch of the template and substrate during separation. The resulting patterned features may be tilted and/or damaged, with the greatest effects often on the smallest features. The separation effects may also have radial dependence. Transition from zones of high feature density to low feature density may also lead to a large number of imprint defects, often the result of a sudden change in shear mismatch between the template and substrate.
Current imprint methods often use templates of arbitrary thickness and shape, as well as arbitrary thickness of wafers and disks (substrates). Also, separation phase imprint parameters like separation forces, tilt, pressures behind template and wafer, vacuum levels, and kinetics of all the above parameters may not be taken into account in current imprint methods with respect to improving the quality of imprinting.